References Frame in Practice Seminar Operational Aspects of GNSS CORS

GNSS CORS for Hydrography

Geoscience, Energy and Maritime Division (GEM)

Salesh Kumar, Hydrographic Surveyor [email protected]

19 September 2018 Suva, Fiji Outline

• Introduction • Work areas at GEM Division • What is hydrography • CORS in hydrography • Some examples • Conclusion

Pacific Community

The Pacific Community (SPC) is the principal scientific and technical organisation in the Pacific region, proudly supporting development since 1947. We are an international development organisation owned and governed by our 26 country and territory members.

The Pacific Community (SPC)

26 Member Countries and Territories

600 staff

14 Sectors

USD 100 million annual budget Our Work Areas What is Hydrography

(26) 6 Idrografia SPOT Inglese - YouTube.MKV

• https://www.youtube.com/watch?v=4YyFowCAA0Y&feature=youtu.be

How can we map the seabed? • Multibeam Echosounder • Singlebeam Echosouders • Sidescan sonars • LiDAR Survey

Vessel, expertise, operational resources, etc.

SPC has all the required toys (~USD 1M) • Singlebeam echosounder, Multibeam echosounder, precision GNSS, sidescan sonar, magnetometer, boomer seismic, software, staff, etc. Suva 1887 Suva 2007 Hydrographic surveying and ocean mapping use high accuracy GPS for three dimensional positioning (X, Y, Z)

Hydrographers interest: Vertical component FIG COMMISSIONS

Positioning of objects in question are: sea surface Water column Seafloor etc

Hydrographic survey Tide Gauge Installation Installation required when there are no permanent tide gauges around the survey areas Usually left in situ for 35 days Tide gauge to pole calibration : o Manual method o GNSS method

Tide Pole to gauge calibration(GNSS method)

• 2 GNSS GPS are used logging at the same time interval (usually 1 sec epoch) • One on a known bench mark • The other on a buoy or any moored boat etc • The data sets are process in RTK Lib software • Chart datums can be established from GPS tide buoys to estimate the mean water surface, relative to the ellipsoid. This datum is used to translate the ellipsoid related bathymetric data to chart datum Hydrographic survey Geodetic survey component Vertical control Method Geometric levelling (Spirit levelling method)

• Levelling are operations which allow the measurement of difference orthometric heights ( or geoid elevations) between points or their difference in elevation. Processing GNSS data AUSPOS processing Post processing (manual method) For centimetric positioning Malo Passage, Luganville, Vanuatu in hydrographic surveying

• based on the integration of GPS and inertial navigation systems (INS). • using a network of GPS base stations to determine ephemeris, clock and atmospheric errors at the rover location. • This technique uses the GPS observations from a Virtual Reference Station to compute a tightly integrated GPS/Inertial solution, with minimum baselines of over 100km. • The PPVRS(post processed virtual reference station) and IAPPK(Inertially aided post- processed kinematic ) methodologies • available in the Applanix POSPac software

Uncharted ship wreck, Luganville Multibeam data of SS President Coolidge

TC PAM – Hazard mapping, SBES Survey Tanna, Vanuatu 25th Nov – 12th Dec 2017

TC PAM – Hazard mapping, UAV and RTK GNSS Survey Tanna, Vanuatu 25th Nov – 12th Dec 2016 Topographic survey

UAV Survey

Consequences of doing nothing in hydrography

• As the reliability of a nautical chart declines it will eventually be removed from publication.

• The lack of digital charting products will see the withdrawal of cruise ships and a decline in tourism.

• Potentially massive impacts on the national and local economies as Hydrographic Services have been shown to have a cost-benefit ratio of more than 1:10 – FOR CRUISE SHIP TOURISM THIS CAN BE 1:200 CONCLUSION

• GPS has been used for horizontal positioning in hydrography for many years.

• CORS data plays a very significant role in Hydrography

• In order to use the vertical component effectively, high-accuracy GPS processing techniques are/must be used

• The more CORS data/stations , the higher the accuracy of our survey data

VINAKA